NASA Curiosity (Mars Rover)

Flyaway

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With Mars Methane Mystery Unsolved, Curiosity Serves Scientists a New One: Oxygen

For the first time in the history of space exploration, scientists have measured the seasonal changes in the gases that fill the air directly above the surface of Gale Crater on Mars. As a result, they noticed something baffling: oxygen, the gas many Earth creatures use to breathe, behaves in a way that so far scientists cannot explain through any known chemical processes.

Over the course of three Mars years (or nearly six Earth years) an instrument in the Sample Analysis at Mars (SAM) portable chemistry lab inside the belly of NASA’s Curiosity rover inhaled the air of Gale Crater and analyzed its composition. The results SAM spit out confirmed the makeup of the Martian atmosphere at the surface: 95% by volume of carbon dioxide (CO2), 2.6% molecular nitrogen (N2), 1.9% argon (Ar), 0.16% molecular oxygen (O2), and 0.06% carbon monoxide (CO). They also revealed how the molecules in the Martian air mix and circulate with the changes in air pressure throughout the year. These changes are caused when CO2 gas freezes over the poles in the winter, thereby lowering the air pressure across the planet following redistribution of air to maintain pressure equilibrium. When CO2 evaporates in the spring and summer and mixes across Mars, it raises the air pressure.

Within this environment, scientists found that nitrogen and argon follow a predictable seasonal pattern, waxing and waning in concentration in Gale Crater throughout the year relative to how much CO2 is in the air. They expected oxygen to do the same. But it didn’t. Instead, the amount of the gas in the air rose throughout spring and summer by as much as 30%, and then dropped back to levels predicted by known chemistry in fall. This pattern repeated each spring, though the amount of oxygen added to the atmosphere varied, implying that something was producing it and then taking it away.

“The first time we saw that, it was just mind boggling,” said Sushil Atreya, professor of climate and space sciences at the University of Michigan in Ann Arbor. Atreya is a co-author of a paper on this topic published on November 12 in the Journal of Geophysical Research: Planets.

As soon as scientists discovered the oxygen enigma, Mars experts set to work trying to explain it. They first double- and triple-checked the accuracy of the SAM instrument they used to measure the gases: the Quadrupole Mass Spectrometer. The instrument was fine. They considered the possibility that CO2 or water (H2O) molecules could have released oxygen when they broke apart in the atmosphere, leading to the short-lived rise. But it would take five times more water above Mars to produce the extra oxygen, and CO2 breaks up too slowly to generate it over such a short time. What about the oxygen decrease? Could solar radiation have broken up oxygen molecules into two atoms that blew away into space? No, scientists concluded, since it would take at least 10 years for the oxygen to disappear through this process.

“We’re struggling to explain this,” said Melissa Trainer, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland who led this research. “The fact that the oxygen behavior isn’t perfectly repeatable every season makes us think that it’s not an issue that has to do with atmospheric dynamics. It has to be some chemical source and sink that we can’t yet account for.”

To scientists who study Mars, the oxygen story is curiously similar to that of methane. Methane is constantly in the air inside Gale Crater in such small quantities (0.00000004% on average) that it’s barely discernable even by the most sensitive instruments on Mars. Still, it’s been measured by SAM’s Tunable Laser Spectrometer. The instrument revealed that while methane rises and falls seasonally, it increases in abundance by about 60% in summer months for inexplicable reasons. (In fact, methane also spikes randomly and dramatically. Scientists are trying to figure out why.)

With the new oxygen findings in hand, Trainer’s team is wondering if chemistry similar to what’s driving methane’s natural seasonal variations may also drive oxygen’s. At least occasionally, the two gases appear to fluctuate in tandem.

“We’re beginning to see this tantalizing correlation between methane and oxygen for a good part of the Mars year,” Atreya said. “I think there’s something to it. I just don’t have the answers yet. Nobody does.”

Oxygen and methane can be produced both biologically (from microbes, for instance) and abiotically (from chemistry related to water and rocks). Scientists are considering all options, although they don’t have any convincing evidence of biological activity on Mars. Curiosity doesn't have instruments that can definitively say whether the source of the methane or oxygen on Mars is biological or geological. Scientists expect that non-biological explanations are more likely and are working diligently to fully understand them.

Trainer’s team considered Martian soil as a source of the extra springtime oxygen. After all, it’s known to be rich in the element, in the form of compounds such as hydrogen peroxide and perchlorates. One experiment on the Viking landers showed decades ago that heat and humidity could release oxygen from Martian soil. But that experiment took place in conditions quite different from the Martian spring environment, and it doesn’t explain the oxygen drop, among other problems. Other possible explanations also don’t quite add up for now. For example, high-energy radiation of the soil could produce extra O2 in the air, but it would take a million years to accumulate enough oxygen in the soil to account for the boost measured in only one spring, the researchers report in their paper.

“We have not been able to come up with one process yet that produces the amount of oxygen we need, but we think it has to be something in the surface soil that changes seasonally because there aren’t enough available oxygen atoms in the atmosphere to create the behavior we see,” said Timothy McConnochie, assistant research scientist at the University of Maryland in College Park and another co-author of the paper.

The only previous spacecraft with instruments capable of measuring the composition of the Martian air near the ground were NASA’s twin Viking landers, which arrived on the planet in 1976. The Viking experiments covered only a few Martian days, though, so they couldn’t reveal seasonal patterns of the different gases. The new SAM measurements are the first to do so. The SAM team will continue to measure atmospheric gases so scientists can gather more detailed data throughout each season. In the meantime, Trainer and her team hope that other Mars experts will work to solve the oxygen mystery.

“This is the first time where we’re seeing this interesting behavior over multiple years. We don’t totally understand it,” Trainer said. “For me, this is an open call to all the smart people out there who are interested in this: See what you can come up with.”

 

Sentinel Chicken

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I have seen photos from the Curiosity Mastcam of sandstone rock layers that are near-identical to sandstone formations I've seen while hiking in Capitol Reef National Park in southern Utah- those layers at Capitol Reef were laid down in wetter times millions of years ago on the Colorado Plateau that probably also occurred on Mars.

But more intriguing to me is the possibility of microbes in the rock varnish layers on Mars- it was only in the last several years that high powered scanning electron microscopes showed microbes in the rock varnish of the Desert Southwest, for years it was thought to be abiotic in origin. I recall an article discussing that the spectroscopic laser on Curiosity hits rock several times but scientists discard the results from the first several hits, but this surface layers may have rock varnish not unlike here on Earth.

I suspect it's a matter of time before we do find microbial life on Mars.
 

sferrin

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I have seen photos from the Curiosity Mastcam of sandstone rock layers that are near-identical to sandstone formations I've seen while hiking in Capitol Reef National Park in southern Utah- those layers at Capitol Reef were laid down in wetter times millions of years ago on the Colorado Plateau that probably also occurred on Mars.

But more intriguing to me is the possibility of microbes in the rock varnish layers on Mars- it was only in the last several years that high powered scanning electron microscopes showed microbes in the rock varnish of the Desert Southwest, for years it was thought to be abiotic in origin. I recall an article discussing that the spectroscopic laser on Curiosity hits rock several times but scientists discard the results from the first several hits, but this surface layers may have rock varnish not unlike here on Earth.

I suspect it's a matter of time before we do find microbial life on Mars.

It would be interesting if they had a common ancestor that hitched a ride from one planet to the other.
 

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NASA press release.

Partway through its last set of activities, Curiosity lost its orientation. Some knowledge of its attitude was not quite right, so it couldn't make the essential safety evaluation. Thus, Curiosity stopped moving, freezing in place until its knowledge of its orientation can be recovered. Curiosity kept sending us information, so we know what happened and can develop a recovery plan. That is exactly what we did today: The engineers on the team built a plan to inform Curiosity of its attitude and to confirm what happened. We want Curiosity to recover its ability to make its safety checks, and we also want to know if there is anything we can do to prevent a similar problem in the future. This approach helps keep our rover safe.

 

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Sols 2653-2655: Attitude Adjustment


"Last Friday’s plan was designed to ensure Curiosity had enough knowledge of its orientation to proceed with arm activities and mobility.
We learned this morning that plan was successful and Curiosity was ready for science once more!
And a very full science plan was made! Much of today’s plan was recycled from last Friday’s intended plan, including contact science with APXS and MAHLI on bedrock targets Moffat Hills and Trossachs. There also was a plethora of ChemCam LIBS targets, a Mastcam mosaic of Western Butte, Mastcam multispectral images on Trossachs, and ENV movies to search for clouds and dust devils while also documenting atmospheric dust levels.
Today’s plan also included a rare measurement with APXS to measure the argon abundance in the atmosphere.
Approximately 25% of Mars’ carbon dioxide-rich atmosphere condenses on the winter polar ice cap, while trace gases like argon do not. This leads to seasonal variations in the relative fraction of argon to carbon dioxide in the air. APXS can measure this argon variation by simply turning on and looking at the sky while the arm is stowed. Seeing argon vary through the year is akin to watching Mars breathe!"
 

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Deposits from giant floods in Gale crater and their implications for the climate of early Mars

Abstract

This study reports in-situ sedimentologic evidence of giant floods in Gale crater, Mars, during the Noachian Period. Features indicative of floods are a series of symmetrical, 10 m-high gravel ridges that occur in the Hummocky Plains Unit (HPU). Their regular spacing, internal sedimentary structures, and bedload transport of fragments as large as 20 cm suggest that these ridges are antidunes: a type of sedimentary structure that forms under very strong flows. Their 150 m wavelength indicates that the north-flowing water that deposited them was at least 24 m deep and had a minimum velocity of 10 m/s. Floods waned rapidly, eroding antidune crests, and re-deposited removed sediments as patches on the up-flow limbs and trough areas between these ridges forming the Striated Unit (SU). Each patch of the SU is 50–200 m wide and long and consists of 5–10 m of south-dipping layers. The strike and dip of the SU layers mimic the attitude of the flank of the antidune on which they were deposited. The most likely mechanism that generated flood waters of this magnitude on a planet whose present-day average temperature is − 60 °C was the sudden heat produced by a large impact. The event vaporized frozen reservoirs of water and injected large amounts of CO2 and CH4 from their solid phases into the atmosphere. It temporarily interrupted a cold and dry climate and generated a warm and wet period. Torrential rainfall occurred planetwide some of which entered Gale crater and combined with water roaring down from Mt. Sharp to cause gigantic flash floods that deposited the SU and the HPU on Aeolis Palus. The warm and wet climate persisted even after the flooding ended, but its duration cannot be determined by our study.

 

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Deposits from giant floods in Gale crater and their implications for the climate of early Mars

Abstract

This study reports in-situ sedimentologic evidence of giant floods in Gale crater, Mars, during the Noachian Period. Features indicative of floods are a series of symmetrical, 10 m-high gravel ridges that occur in the Hummocky Plains Unit (HPU). Their regular spacing, internal sedimentary structures, and bedload transport of fragments as large as 20 cm suggest that these ridges are antidunes: a type of sedimentary structure that forms under very strong flows. Their 150 m wavelength indicates that the north-flowing water that deposited them was at least 24 m deep and had a minimum velocity of 10 m/s. Floods waned rapidly, eroding antidune crests, and re-deposited removed sediments as patches on the up-flow limbs and trough areas between these ridges forming the Striated Unit (SU). Each patch of the SU is 50–200 m wide and long and consists of 5–10 m of south-dipping layers. The strike and dip of the SU layers mimic the attitude of the flank of the antidune on which they were deposited. The most likely mechanism that generated flood waters of this magnitude on a planet whose present-day average temperature is − 60 °C was the sudden heat produced by a large impact. The event vaporized frozen reservoirs of water and injected large amounts of CO2 and CH4 from their solid phases into the atmosphere. It temporarily interrupted a cold and dry climate and generated a warm and wet period. Torrential rainfall occurred planetwide some of which entered Gale crater and combined with water roaring down from Mt. Sharp to cause gigantic flash floods that deposited the SU and the HPU on Aeolis Palus. The warm and wet climate persisted even after the flooding ended, but its duration cannot be determined by our study.


An interesting article, I always thought that Mars was once like the Earth millions of years ago with flowing water on the surface and active volcanoes. This latest discovery will quite possible lead to more speculation about the theory that Mars had at one time had life not the Little Green Men type, more like the single celled organisms that floated in the water.
 

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It will also tell us also a lot about green house effect and how an habitable planet can loose much of its atmosphere...
 

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First You See It, Then You Don’t: Scientists Closer to Explaining Mars Methane Mystery
Jun 29, 2021

Why do some science instruments detect the gas on the Red Planet while others don’t?
Reports of methane detections at Mars have captivated scientists and non-scientists alike. On Earth, a significant amount of methane is produced by microbes that help most livestock digest plants. This digestion process ends with livestock exhaling or burping the gas into the air.

While there are no cattle, sheep, or goats on Mars, finding methane there is exciting because it may imply that microbes were, or are, living on the Red Planet. Methane could have nothing to do with microbes or any other biology, however; geological processes that involve the interaction of rocks, water, and heat can also produce it.

Before identifying the sources of methane on Mars, scientists must settle a question that’s been gnawing at them: Why do some instruments detect the gas while others don’t? NASA’s Curiosity rover, for instance, has repeatedly detected methane right above the surface of Gale Crater. But ESA’s (the European Space Agency) ExoMars Trace Gas Orbiter hasn’t detected any methane higher in the Martian atmosphere.

“When the Trace Gas Orbiter came on board in 2016, I was fully expecting the orbiter team to report that there’s a small amount of methane everywhere on Mars,” said Chris Webster, lead of the Tunable Laser Spectrometer (TLS) instrument in the Sample Analysis at Mars (SAM) chemistry lab aboard the Curiosity rover.

The TLS has measured less than one-half part per billion in volume of methane on average in Gale Crater. That’s equivalent to about a pinch of salt diluted in an Olympic-size swimming pool. These measurements have been punctuated by baffling spikes of up to 20 parts per billion in volume.

“But when the European team announced that it saw no methane, I was definitely shocked,” said Webster, who’s based at NASA’s Jet Propulsion Laboratory in Southern California.

The European orbiter was designed to be the gold standard for measuring methane and other gases over the whole planet. At the same time, Curiosity’s TLS is so precise, it will be used for early warning fire detection on the International Space Station and for tracking oxygen levels in astronaut suits. It’s also been licensed for use at power plants, on oil pipelines, and in fighter aircraft, where pilots can monitor the oxygen and carbon dioxide levels in their face masks.

Still, Webster and the SAM team were jolted by the European orbiter findings and immediately set out to scrutinize the TLS measurements on Mars.

Some experts suggested that the rover itself was releasing the gas. “So we looked at correlations with the pointing of the rover, the ground, the crushing of rocks, the wheel degradation – you name it,” Webster said. “I cannot overstate the effort the team has put into looking at every little detail to make sure those measurements are correct, and they are.”

Webster and his team reported their results today in the Astronomy & Astrophysics journal.

As the SAM team worked to confirm its methane detections, another member of Curiosity’s science team, planetary scientist John E. Moores from York University in Toronto, published an intriguing prediction in 2019. “I took what some of my colleagues are calling a very Canadian view of this, in the sense that I asked the question: ‘What if Curiosity and the Trace Gas Orbiter are both right?’” Moores said.

Moores, as well as other Curiosity team members studying wind patterns in Gale Crater, hypothesized that the discrepancy between methane measurements comes down to the time of day they’re taken. Because it needs a lot of power, TLS operates mostly at night when no other Curiosity instruments are working. The Martian atmosphere is calm at night, Moores noted, so the methane seeping from the ground builds up near the surface where Curiosity can detect it.

The Trace Gas Orbiter, on the other hand, requires sunlight to pinpoint methane about 3 miles, or 5 kilometers, above the surface. “Any atmosphere near a planet’s surface goes through a cycle during the day,” Moores said. Heat from the Sun churns the atmosphere as warm air rises and cool air sinks. Thus, the methane that is confined near the surface at night is mixed into the broader atmosphere during the day, which dilutes it to undetectable levels. “So I realized no instrument, especially an orbiting one, would see anything,” Moores said.

Immediately, the Curiosity team decided to test Moores’ prediction by collecting the first high-precision daytime measurements. TLS measured methane consecutively over the course of one Martian day, bracketing one nighttime measurement with two daytime ones. With each experiment, SAM sucked in Martian air for two hours, continuously removing the carbon dioxide, which makes up 95% of the planet’s atmosphere. This left a concentrated sample of methane that TLS could easily measure by passing an infrared laser beam through it many times, one that’s tuned to use a precise wavelength of light that is absorbed by methane.

“John predicted that methane should effectively go down to zero during the day, and our two daytime measurements confirmed that,” said Paul Mahaffy, the principal investigator of SAM, who’s based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. TLS’ nighttime measurement fit neatly within the average the team had already established. “So that’s one way of putting to bed this big discrepancy,” Mahaffy said.

While this study suggests that methane concentrations rise and fall throughout the day at the surface of Gale Crater, scientists have yet to solve the global methane puzzle at Mars. Methane is a stable molecule that is expected to last on Mars for about 300 years before getting torn apart by solar radiation. If methane is constantly seeping from all similar craters, which scientists suspect is likely given that Gale doesn’t seem to be geologically unique, enough of it should have accumulated in the atmosphere for the Trace Gas Orbiter to detect. Scientists suspect that something is destroying methane in less than 300 years.

Experiments are underway to test whether very low-level electric discharges induced by dust in the Martian atmosphere could destroy methane, or whether abundant oxygen at the Martian surface quickly destroys methane before it can reach the upper atmosphere.

“We need to determine whether there’s a faster destruction mechanism than normal to fully reconcile the data sets from the rover and the orbiter,” Webster said.

News Media Contact

Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-2433
andrew.c.good@jpl.nasa.gov
Written by Lonnie Shekhtman
NASA’s Goddard Space Flight Center, Greenbelt, Md.

2021-130
 

Flyaway

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Freely accessible article:

'Alien burp' may have been detected by NASA's Curiosity rover


Related paper:

Mars Methane Sources in Northwestern Gale Crater Inferred from Back-Trajectory Modeling

Abstract
During its five years of operation, the Sample Analysis at Mars (SAM) Tunable Laser Spectrometer (TLS) on board the Curiosity rover has detected six methane spikes above a low background abundance in Gale crater. The methane spikes are likely the consequence of nearby surface emission. Here we use inverse Lagrangian modeling techniques to identify probable upstream emission regions for these methane spikes at an unprecedented spatial resolution. Inside Gale crater, the northwestern crater floor casts the strongest influence on the detections. Outside Gale crater, the emission region with the strongest influence extends towards the north. The contrasting results from two consecutive methane measurements point to an active emission region to the west and the southwest of the Curiosity rover on the northwestern crater floor. The observed spike magnitude and frequency also favor emission sites on the northwestern crater floor, unless fast methane removal mechanisms that are unknown to date are at work.

 

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